In order to make oil for human consumption, various products are "squeezed" (in some cases, this process is mechanical, in others, it is chemical) to access the oil. Olives, corn, soy, palm nuts, etc can all be sources of oil. Have you ever seen the remains of that process sold? No, likely not. Those remains are sold to farmers as food for their cows, pigs, chickens, fish, etc. The oil is expensive, the remains are cheap. Every time you use oil, you subsidize the livestock industries.